Electrocatalysts For Hydrogen Oxidation Reaction Research Articles

One‐Step Synthesis of W2C@N,P‐C Nanocatalysts for Efficient Hydrogen Electrooxidation across the Whole pH Range

AbstractHighly active and low‐cost non‐noble metal electrocatalysts for hydrogen oxidation reaction (HOR) are crucial for the large‐scale applications of fuel cells, which, unfortunately, are rarely documented up to now. Here, a facile one‐step strategy to fabricate W2C nanoparticles (≈3 nm) encased in N, P‐doped few layer carbon materials (W2C@N,P‐C, WNPC) as an efficient non‐noble metal HOR electrocatalyst simply by calcining the mixture of recrystallized phosphotungstic acid and dicyandiamide is reported. The obtained WNPC catalyst shows extraordinarily high HOR activities (1.03/0.91/0.84 mA cm−2 at 0.05 V vs reversible hydrogen electrode in 0.1 m HClO4/0.1 m KOH/0.1 m neutral phosphate buffered saline electrolytes, respectively), excellent durability during accelerated degradation tests for 10 000 cycles, and outstanding CO tolerance. These high performances are attributed to the uniform structure of WNPC, and more essentially, the synergistic effect among N, P, and C species which elevates the reducibility of WNPC, favoring the generation of abundant HOR active sites.

Exploring the Composition–Activity Relation of Ni–Cu Binary Alloy Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Media

The development of nonprecious electrocatalysts for hydrogen oxidation reaction (HOR) in alkaline is becoming one of the major obstacles to alkaline polymer electrolyte fuel cells (APEFCs). In this work, a series of Ni–Cu binary alloy films are high-throughput prepared using a combinatorial magnetron cosputtering method, and their corresponding electrocatalytic performances toward HOR in alkaline media are systematically studied. Both the intrinsic activity and antioxidation property of Ni are remarkably enhanced after Cu doping. A volcano-type relation between HOR activity and Cu doping content is revealed. The maximum activity is found at ca. 40 at. % Cu, with the exchange current density 4 times higher than that of pure Ni. This study gives us a deeper understanding of the impact of Cu addition on the HOR catalytic activity of Ni.

Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolytes

In the past 5 years, advances in anion-conductive membranes have opened the door for the development of advanced anion-exchange membrane fuel cells (AEMFCs) as the next generation of affordable fuel cells. Several recent works have shown that AEMFCs currently achieve nearly identical beginning-of-life performance as state-of-the-art proton exchange membrane fuel cells. However, until now, these high AEMFC performances have been reached with platinum-group metal (PGM)-based anode and cathode catalysts. In order to fulfill the potential of AEMFCs, such catalysts should in the near future be free of PGMs and, eventually, free of critical raw materials. Although great progress has been achieved in the development of PGM-free catalysts for the oxygen reduction reaction in basic media, significantly less attention has been paid to the catalysis of the hydrogen oxidation reaction (HOR). The much lower HOR activity of Pt in basic media compared with that in acid was itself revealed only relatively recently. While...

Development of Ni-Based Bimetallic Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Fuel Cells

Anion exchange membrane fuel cells (AEMFCs) opens up the possibility of using non-platinum and/or non-platinum group metals (PGM) as electrocatalysts for both hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR). However, the slow kinetics of HOR along with the current lack of a durable and highly conducting OH- ion membrane remain major bottlenecks limiting its practical application. HOR with PGM free catalysts are still in the early stages of research unlike ORR with non-PGM catalysts1 . In order to overcome this limitation it is important to understand the mechanism of the HOR on the surface of the electro catalysts. It is considered that the two main descriptors, which enhance the electrocatalytic activity of the HOR, are the OHad or Had molecules on the surface of the catalytic materials.2,3 Ni and its alloys with transition metals would be one of the alternative choices for the HOR as Raney Ni and some of the Ni based alloys have been found showing improved HOR activity.4 Morphology, size and surface of the metallic nanoparicles have significant role on the catalytic activity in their respective applications. In this work we have synthesized monodispersed NiCo, NiCu and NiFe based bimetallic alloy nanoparticles of less than 20 nm size by high temperature solvothermal process.5 The synthesized alloy nanoparticles have been evaluated for their electrocatalytic activity and stability towards the HOR in a conventional rotating disk electrode (RDE) configuration tehnique. The nanoparticles have also been characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) to understand their physicochemical properties. The effect of surface state and alloying of the nanoparticles on the HOR kinetics is studied and analyzed in terms of mechanism and reaction steps involved. Our overall ambition in this work is to explore PGM free bi and trimetallic nanoparticles (NiM and NiMN) for the HOR and use them as anode catalysts in an operating AEM fuel cells. References Zhuang, Z. et al. Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte. Nat.Commun. 7, 10141(2016).Strmcnik, D. et al. Improving the hydrogen oxidation reaction rate by promotion of hydroxyl adsorption. Nat.chem. 5,300-306 (2013).Parsons, R.The rate of electrolytic hydrogen evolution and the heat of adsorption of hydrogen.Trans. Faraday Soc. 54, 1053–1063 (1958).Kabir, S. et al. Platinum group metal-free NiMo hydrogen oxidation catalysts: high performance and durability in alkaline exchange membrane fuel cells. Jour.Mater.Chem. A, (2017).Carenco,S. et al.Controlled design of size-tunable monodisperse nickel nanoparticles.Chem.Mater.22,1340-1349(2010). Figure 1:Representative bright field scanning transmission electron microscopy (STEM) image of bimetallic NiCo nanoparticles Figure 1

Infiltrated Pr2NiO4 as promising bi-electrode for symmetrical solid oxide fuel cells

In-situ growth of nanoparticles on electrode surface for high temperature energy conversion devices is one of efficient ways for new electro-catalyst design. Here, perovskite-related Pr2NiO4 (PNO) has been evaluated as a novel symmetrical electrode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Nickel nanoparticles are exsolved and dispersed on the surface of PNO after exposed in H2 at 800 °C as an efficient electrocatalyst for hydrogen oxidation reaction (HOR) as anode. The electro-activity towards oxygen reduction reaction (ORR) at cathode side is further improved by infiltration process. A synergetic effect of in-situ exsolved nanoparticles as well as infiltrated ionic conducting particles have improved HOR and ORR activity at anode and cathode side, respectively. Furthermore, symmetrical SOFC (SSOFC) with infiltrated Pr2NiO4 as bi-electrode exhibits excellent short-term stability and reliable redox stability in repeated H2/air cycles.

Ni-Based Hydrogen Oxidation Reaction Electrocatalysts for Alkaline Anion-Exchange Membrane Fuel Cells: Systematic Study on the Doping Effect

Recent developments in hydroxide conducting anion exchange membranes have contributed to the growing interest in alkaline anion exchange membrane fuel cells (AEMFC) which has the potential to be the next fuel cell generation as in principle this technology allows to replace platinum-based catalysts for affordable metal catalysts. Until now, there are a few research studies describing initial development of hydrogen fueled AEMFC [1], and practically no work done on completely platinum group metal (PGM)-free catalysts for AEMFC. Though some progress was made in the development of low cost electrocatalysts for oxygen reduction reaction (ORR) in base media [2], much less attention was paid to the electrocatalysis for hydrogen oxidation reaction (HOR) in alkaline solutions. Attempts to move away from the use of PGMs results in prohibitively large voltage losses on the anode in the base media (Fig. 1). This work provides an extensive literature review on both theoretical and experimental advances in HOR electrocatalysts for AEMFCs. In addition, this work provides new insights into new Ni-based electrocatalysts for the HOR in alkaline medium that are being developed in our group at the Technion, including RDE, XRD, XPS, TPD/TPR/TPO, SEM results and some aspects of DFT calculations. [1] H.A. Miller et al. Angew. Chem. Int. Ed. 55 (2016) 6004. [2] M.R. Tarasevich et. al. Russ. J. Electrochem. 52 (2016) 193. [3] E.S. Davydova et. al. (2017), in preparation. [4] Zhuang Z. et al. Nat. Commun. 7 (2016) 10141. [5] Zheng J. et. al. Sci. Adv. 2 (2016) e1501602. [6] http://www.infomine.com/Acknowledgements. This work was partially funded by the Grand Technion Energy Program (GTEP), by the European Union's Horizon 2020 research and innovation programme under grant agreement No 721065, by the Ministry of Science, Technology & Space of Israel through the M.era-NET Transnational Call 2015, NEXTGAME project grant 3-12948, by the Ministry of National Infrastructure, Energy and Water Resources of Israel, and by the 2nd Israel National Research Center for Electrochemical Propulsion (INREP2-ISF). Figure 1

A Facile <i>In Situ</i> Synthesis of Carbon Supported Nickel Phosphide (Ni<sub>5</sub>P<sub>4</sub>@C) and Application as Hydrogen Oxidation Reaction Catalyst in Alkaline Electrolyte

Monodisperse nickel phosphide (Ni5P4) nanoparticles supported on carbon (Ni5P4@C) were in situ synthesized by one step solution-phase route, in which the mixture of trioctyloxide (TOPO) and trioctylphosphine (TOP) was used as solvent, capping agent and phosphor source. Ni5P4nanocrystals were in situ coupled by active carbon simply adding the carbon to the reaction solution. The as-prepared Pt-free Ni5P4 nanocrystals exhibit the enhanced electrocatalytic activity toward hydrogen oxidation reaction (HOR) compared to pure commercial Ni nanoparticles. Therefore, the obtained Ni5P4@C nanocatalyst appears to be promising non precious metal electrocatalysts for HOR.

Palladium/nickel bifunctional electrocatalyst for hydrogen oxidation reaction in alkaline membrane fuel cell

Investigation of the hydrogen oxidation reaction (HOR) in alkaline media has been pursued in the past few years side by side with the development of alkaline membrane fuel cells (AMFCs), also called anion exchange membrane fuel cells (AEM-FCs). In this communication, we present the synthesis, electrochemistry and AMFC test of a platinum-free HOR catalyst. The anode catalyst is prepared by growing palladium nanoparticles onto nanoparticles of an oxophilic metal (nickel), resulting in nano-dispersed, interconnected crystalline phases of Ni and Pd. When used in the anode of a hydrogen/air AMFC, such Pd/Ni catalyst exhibits high HOR activity, resulting in record high performance for a platinum-free AMFC (0.4 A cm−2 at 0.6 V vs RHE). The enhancement of HOR catalytic activity vs. that observed at Pd (or Ni) alone is revealed directly in rotating disc electrode tests of this Pd/Ni catalyst that shows a significant negative shift (200 mV) of the onset potential for the HOR current vs. the case of Pd.

Invited: Non-Precious Metal Electrocatalysts: Accomplishments and Challenges

With increasing demand for energy, the development of the energy storage and conversion technologies has become the focus of an intensive research effort in recent years. Among various technologies, fuel cells, batteries, supercapacitors, and water electrolyzers have been recognized as potentially feasible and efficient devices for portable, stationary, and transportation applications. For both the fuel cells and metal-air batteries, the oxygen reduction reaction (ORR) cathode catalysts play a major role in the device performance characteristics, as determined based on the power output, open circuit voltage, charge-discharge rate, energy efficiency, cycling life (for batteries), etc. Currently, Pt-nanoparticle catalysts, supported on high surface-area carbons, represent the state-of-the-art electrocatalysts for hydrogen oxidation reaction (HOR) and ORR at the polymer electrolyte fuel cell (PEFC) anode and cathode, respectively. However, the prohibitive price and scarcity of Pt have limited its widespread implementation in the PEFC, especially at the cathode, which accounts for approximately 80% of the Pt loading in fuel cells. As a result, non-precious metal catalysts (NPMCs) for the ORR have received more attention in recent years as a possible replacement of precious-metal catalysts.A successful ORR catalyst must combine high activity with good long-term stability – a major challenge in the strongly acidic environment of the PEFC cathode. Since the early work of Jasinski in the 1960s (Nature 201, 1212, 1964), recent breakthroughs in the synthesis of high-performance non-precious metal catalysts (NPMCs) (e.g., Lefèvre et al., Science 324, 71, 2009; Wu et al., Science 332, 443, 2011) make replacement of Pt in ORR electrocatalysts with earth-abundant elements, such as Fe, Co, N, and C, a realistic possibility, though the activity and especially durability of the resulting catalysts need to be improved before the technology can become viable.The NPMC performance depends on the selection of precursors, the synthesis chemistry; and especially the catalyst nanostructure. In addition to those, the CNx structures likely play a major role in the performance of ORR active site(s). Apart from possible direct participation in the active site, the transition metal is crucial to in-situ formation of carbon nanostructures (nanotubes, onion-like structures, graphene) by catalyzing the decomposition of the nitrogen/carbon precursor(s) at a high temperatures (800-1000°C). The formation of different carbon and nitrogen-doped carbon nanostructures can be controlled during the synthesis of such NPMCs. The highly-graphitized carbon nanostructures likely serve as a matrix for the formation of the ORR-active groups with improved catalytic activity and durability, containing nitrogen and possibly also metal atoms.Future NPMC synthesis approaches are certain to focus on the precise control of interactions between precursors of the metal and carbon/nitrogen during the heat treatment, with the main purpose being the maximizations of the population of active sites, optimization of nitrogen doping levels, and generation of carbon morphologies capable of hosting active and stable ORR sites. This is evident not only in catalysts developed for PEFCs but also in materials specifically designed for alkaline fuel cells (Chung et al., Nat. Commun. 4:1922 doi:10.1038/ncomms2944, 2013). In the end, however, the much needed progress in ORR electrocatalysis at NPMCs, especially in acid media, will be decided by better understanding of the origin of the NPMC activity and the nature of the active site. That key part of NPMC development will be addressed in this presentation along with the summary of the progress achieved to date and challenges still awaiting non-precious metal electrocatalysis in polymer electrolyte fuel cells. Acknowledgment Financial support from DOE-EERE Fuel Cell Technologies Office and Los Alamos National Laboratory Laboratory-Directed Research and Development (LDRD) Program and is gratefully acknowledged.

Electrospun Pt/SnO2 nanofibers as an excellent electrocatalysts for hydrogen oxidation reaction with ORR-blocking characteristic

Abstract Pt/SnO 2 nanofibers were synthesized via electrospinning. The unique electrochemical properties were in evidence based on the activity that allowed a hydrogen oxidation reaction and inhibit an oxygen reduction reaction. A high electrochemically active surface area value of 81.17 m 2 /g-Pt was achieved with ultra-low Pt loading (4.03 wt.%). The kinetics of a hydrogen oxidation reaction was investigated using a linear sweep voltammetry technique under a hydrogen atmosphere. A diffusion-limited current was achieved at 0.07 V and was stable at a high potential. This preparation technique shows great promise for the design of anode electrocatalyst material for fuel cells.

Pt–W bimetallic alloys as CO-tolerant PEMFC anode catalysts

Pt–W nanoalloys with compositions ranging from Pt3W to PtW2 were explored as electrocatalysts for hydrogen oxidation reaction (HOR). It is shown that alloying Pt with W can lead to significantly enhanced electrocatalytic activity for HOR, with nearly 4 times increase in the exchange current density as compared with pure Pt. What's more, these Pt–W alloys possess superior CO tolerance to Pt and PtRu, mainly due to the weakened bonding of CO on their Pt-enriched surfaces.

Synthesis and Characterization of Pt-Carbon Nano Capsule Electrocatalyst for Hydrogen Oxidation Reaction

not Available.

Synthesis and Characterization of Pt-Carbon Nano Capsule Electrocatalyst for Hydrogen Oxidation Reaction

Synthesis of nanoparticulate Pt and PtRu were conducted in typical wet chemical approach on carbon nanocapsules (CNCs) and VXC72R for electrochemical characterization in acidic electrolyte. XRD of the as-synthesized powders indicated Pt and PtRu in FCC phase with particle sizes around 2~15 nm. Cyclic voltammetry of Pt/CNCs and PtRu/CNCs was analyzed for hydrogen oxidation reaction, revealing impressive catalytic power. In contrast, Pt/VXC72R and PtRu/VXC72R demonstrated moderately reduced performance. Our work suggested CNCs to be superb material as electrocatalyst support.